Christina Aguilera sure knows how to keep a secret. Aside from refusing to confirm her very obvious pregnancy, the singer apparently knows the sex of her baby — but is keeping it mum from the public. The mom-to-be shopped at the posh Bel Bambini store in West Hollywood this Saturday with her husband, Jordan Bratman, her mother-in-law and her sister-in-law. Christina spent two hours picking out items for her baby registry, including blankets, diaper bags, bottles and clothing. "They registered for all the accessories," store employee Crysta Smith told People. "She had a little bump. She said she was so excited." She also told the staff the baby's gender, but asked them to keep it private. Looks like the guessing game has turned from "Is she or isn't she?" to "Boy or girl?"